aboutsummaryrefslogtreecommitdiff
path: root/block/qcow2-cluster.c
AgeCommit message (Collapse)Author
2023-11-08qcow2: Take locks for accessing bs->fileKevin Wolf
This updates the qcow2 code to add GRAPH_RDLOCK annotations for all places that read bs->file. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-ID: <20231027155333.420094-22-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-11-06qcow2: keep reference on zeroize with discard-no-unref enabledJean-Louis Dupond
When the discard-no-unref flag is enabled, we keep the reference for normal discard requests. But when a discard is executed on a snapshot/qcow2 image with backing, the discards are saved as zero clusters in the snapshot image. When committing the snapshot to the backing file, not discard_in_l2_slice is called but zero_in_l2_slice. Which did not had any logic to keep the reference when discard-no-unref is enabled. Therefor we add logic in the zero_in_l2_slice call to keep the reference on commit. Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1621 Signed-off-by: Jean-Louis Dupond <jean-louis@dupond.be> Message-Id: <20231003125236.216473-2-jean-louis@dupond.be> [hreitz: Made the documentation change more verbose, as discussed on-list] Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
2023-10-12qcow2: Mark qcow2_signal_corruption() and callers GRAPH_RDLOCKKevin Wolf
This adds GRAPH_RDLOCK annotations to declare that callers of qcow2_signal_corruption() need to hold a reader lock for the graph because it calls bdrv_get_node_name(), which accesses the parents list of a node. For some places, we know that they will hold the lock, but we don't have the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock() with a FIXME comment. These places will be removed once everything is properly annotated. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-ID: <20230929145157.45443-15-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-06-28block: use bdrv_co_debug_event in coroutine contextPaolo Bonzini
bdrv_co_debug_event was recently introduced, with bdrv_debug_event becoming a wrapper for use in unknown context. Because most of the time bdrv_debug_event is used on a BdrvChild via the wrapper macro BLKDBG_EVENT, introduce a similar macro BLKDBG_CO_EVENT that calls bdrv_co_debug_event, and switch whenever possible. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20230601115145.196465-13-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-06-28qcow2: mark more functions as coroutine_fns and GRAPH_RDLOCKPaolo Bonzini
Mark functions as coroutine_fn when they are only called by other coroutine_fns and they can suspend. Change calls to co_wrappers to use the non-wrapped functions, which in turn requires adding GRAPH_RDLOCK annotations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20230601115145.196465-11-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-06-05qcow2: add discard-no-unref optionJean-Louis Dupond
When we for example have a sparse qcow2 image and discard: unmap is enabled, there can be a lot of fragmentation in the image after some time. Especially on VM's that do a lot of writes/deletes. This causes the qcow2 image to grow even over 110% of its virtual size, because the free gaps in the image get too small to allocate new continuous clusters. So it allocates new space at the end of the image. Disabling discard is not an option, as discard is needed to keep the incremental backup size as low as possible. Without discard, the incremental backups would become large, as qemu thinks it's just dirty blocks but it doesn't know the blocks are unneeded. So we need to avoid fragmentation but also 'empty' the unneeded blocks in the image to have a small incremental backup. In addition, we also want to send the discards further down the stack, so the underlying blocks are still discarded. Therefor we introduce a new qcow2 option "discard-no-unref". When setting this option to true, discards will no longer have the qcow2 driver relinquish cluster allocations. Other than that, the request is handled as normal: All clusters in range are marked as zero, and, if pass-discard-request is true, it is passed further down the stack. The only difference is that the now-zero clusters are preallocated instead of being unallocated. This will avoid fragmentation on the qcow2 image. Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1621 Signed-off-by: Jean-Louis Dupond <jean-louis@dupond.be> Message-Id: <20230605084523.34134-2-jean-louis@dupond.be> Reviewed-by: Hanna Czenczek <hreitz@redhat.com> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
2023-04-25qcow2: mark various functions as coroutine_fn and GRAPH_RDLOCKPaolo Bonzini
Functions that can do I/O (including calling bdrv_is_allocated and bdrv_block_status functions) are prime candidates for being coroutine_fns. Make the change for those that are themselves called only from coroutine_fns. Also annotate that they are called with the graph rdlock taken, thus allowing them to call bdrv_co_*() functions for I/O. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20230309084456.304669-9-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-02-23block: Mark public read/write functions GRAPH_RDLOCKKevin Wolf
This adds GRAPH_RDLOCK annotations to declare that callers of bdrv_co_pread*/pwrite*() need to hold a reader lock for the graph. For some places, we know that they will hold the lock, but we don't have the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock() with a FIXME comment. These places will be removed once everything is properly annotated. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20230203152202.49054-12-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-02-23block: Mark read/write in block/io.c GRAPH_RDLOCKKevin Wolf
This adds GRAPH_RDLOCK annotations to declare that callers of bdrv_driver_*() need to hold a reader lock for the graph. It doesn't add the annotation to public functions yet. For some places, we know that they will hold the lock, but we don't have the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock() with a FIXME comment. These places will be removed once everything is properly annotated. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20230203152202.49054-11-kwolf@redhat.com> Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-01-20include/block: Untangle inclusion loopsMarkus Armbruster
We have two inclusion loops: block/block.h -> block/block-global-state.h -> block/block-common.h -> block/blockjob.h -> block/block.h block/block.h -> block/block-io.h -> block/block-common.h -> block/blockjob.h -> block/block.h I believe these go back to Emanuele's reorganization of the block API, merged a few months ago in commit d7e2fe4aac8. Fortunately, breaking them is merely a matter of deleting unnecessary includes from headers, and adding them back in places where they are now missing. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221221133551.3967339-2-armbru@redhat.com>
2022-10-27qcow2: switch to *_co_* functionsAlberto Faria
Signed-off-by: Alberto Faria <afaria@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20221013123711.620631-20-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-10-27qcow2: manually add more coroutine_fn annotationsPaolo Bonzini
The validity of these was double-checked with Alberto Faria's static analyzer. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20221013123711.620631-13-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-10-07qcow2: add missing coroutine_fn annotationsPaolo Bonzini
Callers of coroutine_fn must be coroutine_fn themselves, or the call must be within "if (qemu_in_coroutine())". Apply coroutine_fn to functions where this holds. Reviewed-by: Alberto Faria <afaria@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20220922084924.201610-15-pbonzini@redhat.com> [kwolf: Fixed up coding style] Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2022-07-12block: Change bdrv_{pread,pwrite,pwrite_sync}() param orderAlberto Faria
Swap 'buf' and 'bytes' around for consistency with bdrv_co_{pread,pwrite}(), and in preparation to implement these functions using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pread(child, offset, buf, bytes, flags) + bdrv_pread(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite(child, offset, buf, bytes, flags) + bdrv_pwrite(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite_sync(child, offset, buf, bytes, flags) + bdrv_pwrite_sync(child, offset, bytes, buf, flags) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-3-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-07-12block: Add a 'flags' param to bdrv_{pread,pwrite,pwrite_sync}()Alberto Faria
For consistency with other I/O functions, and in preparation to implement them using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes; @@ - bdrv_pread(child, offset, buf, bytes) + bdrv_pread(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite(child, offset, buf, bytes) + bdrv_pwrite(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite_sync(child, offset, buf, bytes) + bdrv_pwrite_sync(child, offset, buf, bytes, 0) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-2-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-03-07osdep: Move memalign-related functions to their own headerPeter Maydell
Move the various memalign-related functions out of osdep.h and into their own header, which we include only where they are used. While we're doing this, add some brief documentation comments. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-id: 20220226180723.1706285-10-peter.maydell@linaro.org
2021-10-15qcow2: Silence clang -m32 compiler warningHanna Reitz
With -m32, size_t is generally only a uint32_t. That makes clang complain that in the assertion assert(qiov->size <= INT64_MAX); the range of the type of qiov->size (size_t) is too small for any of its values to ever exceed INT64_MAX. Cast qiov->size to uint64_t to silence clang. Fixes: f7ef38dd1310d7d9db76d0aa16899cbc5744f36d ("block: use int64_t instead of uint64_t in driver read handlers") Signed-off-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20211011155031.149158-1-hreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
2021-09-29block: use int64_t instead of uint64_t in driver read handlersVladimir Sementsov-Ogievskiy
We are generally moving to int64_t for both offset and bytes parameters on all io paths. Main motivation is realization of 64-bit write_zeroes operation for fast zeroing large disk chunks, up to the whole disk. We chose signed type, to be consistent with off_t (which is signed) and with possibility for signed return type (where negative value means error). So, convert driver read handlers parameters which are already 64bit to signed type. While being here, convert also flags parameter to be BdrvRequestFlags. Now let's consider all callers. Simple git grep '\->bdrv_\(aio\|co\)_preadv\(_part\)\?' shows that's there three callers of driver function: bdrv_driver_preadv() in block/io.c, passes int64_t, checked by bdrv_check_qiov_request() to be non-negative. qcow2_load_vmstate() does bdrv_check_qiov_request(). do_perform_cow_read() has uint64_t argument. And a lot of things in qcow2 driver are uint64_t, so converting it is big job. But we must not work with requests that don't satisfy bdrv_check_qiov_request(), so let's just assert it here. Still, the functions may be called directly, not only by drv->... Let's check: git grep '\.bdrv_\(aio\|co\)_preadv\(_part\)\?\s*=' | \ awk '{print $4}' | sed 's/,//' | sed 's/&//' | sort | uniq | \ while read func; do git grep "$func(" | \ grep -v "$func(BlockDriverState"; done The only one such caller: QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, &data, 1); ... ret = bdrv_replace_test_co_preadv(bs, 0, 1, &qiov, 0); in tests/unit/test-bdrv-drain.c, and it's OK obviously. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20210903102807.27127-4-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> [eblake: fix typos] Signed-off-by: Eric Blake <eblake@redhat.com>
2021-09-15qcow2: introduce qcow2_parse_compressed_l2_entry() helperVladimir Sementsov-Ogievskiy
Add helper to parse compressed l2_entry and use it everywhere instead of open-coding. Note, that in most places we move to precise coffset/csize instead of sector-aligned. Still it should work good enough for updating refcounts. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20210914122454.141075-4-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-15qcow2: compressed read: simplify cluster descriptor passingVladimir Sementsov-Ogievskiy
Let's pass the whole L2 entry and not bother with L2E_COMPRESSED_OFFSET_SIZE_MASK. It also helps further refactoring that adds generic qcow2_parse_compressed_l2_entry() helper. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20210914122454.141075-3-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-15qcow2: handle_dependencies(): relax conflict detectionVladimir Sementsov-Ogievskiy
There is no conflict and no dependency if we have parallel writes to different subclusters of one cluster when the cluster itself is already allocated. So, relax extra dependency. Measure performance: First, prepare build/qemu-img-old and build/qemu-img-new images. cd scripts/simplebench ./img_bench_templater.py Paste the following to stdin of running script: qemu_img=../../build/qemu-img-{old|new} $qemu_img create -f qcow2 -o extended_l2=on /ssd/x.qcow2 1G $qemu_img bench -c 100000 -d 8 [-s 2K|-s 2K -o 512|-s $((1024*2+512))] \ -w -t none -n /ssd/x.qcow2 The result: All results are in seconds ------------------ --------- --------- old new -s 2K 6.7 ± 15% 6.2 ± 12% -7% -s 2K -o 512 13 ± 3% 11 ± 5% -16% -s $((1024*2+512)) 9.5 ± 4% 8.4 -12% ------------------ --------- --------- So small writes are more independent now and that helps to keep deeper io queue which improves performance. 271 iotest output becomes racy for three allocation in one cluster. Second and third writes may finish in different order. Second and third requests don't depend on each other any more. Still they both depend on first request anyway. Filter out second and third write offsets to cover both possible outputs. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20210824101517.59802-4-vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> [hreitz: s/ an / and /] Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2021-09-15qcow2: refactor handle_dependencies() loop bodyVladimir Sementsov-Ogievskiy
No logic change, just prepare for the following commit. While being here do also small grammar fix in a comment. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Message-Id: <20210824101517.59802-3-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2020-11-24qcow2: Fix corruption on write_zeroes with MAY_UNMAPMaxim Levitsky
Commit 205fa50750 ("qcow2: Add subcluster support to zero_in_l2_slice()") introduced a subtle change to code in zero_in_l2_slice: It swapped the order of 1. qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 2. set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO); 3. qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); To 1. qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice); 2. qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); 3. set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO); It seems harmless, however the call to qcow2_free_any_clusters can trigger a cache flush which can mark the L2 table as clean, and assuming that this was the last write to it, a stale version of it will remain on the disk. Now we have a valid L2 entry pointing to a freed cluster. Oops. Fixes: 205fa50750 ("qcow2: Add subcluster support to zero_in_l2_slice()") Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> [ kwolf: Fixed to restore the correct original order from before 205fa50750; added comments like in discard_in_l2_slice(). ] Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20201124092815.39056-1-kwolf@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-11-09qcow2: Document and enforce the QCowL2Meta invariantsAlberto Garcia
The QCowL2Meta structure is used to store information about a part of a write request that touches clusters that need changes in their L2 entries. This happens with newly-allocated clusters or subclusters. This structure has changed a bit since it was first created and its current documentation is not quite up-to-date. A write request can span a region consisting of a combination of clusters of different types, and qcow2_alloc_host_offset() can repeatedly call handle_copied() and handle_alloc() to add more clusters to the mix as long as they all are contiguous on the image file. Because of this a write request has a list of QCowL2Meta structures, one for each part of the request that needs changes in the L2 metadata. Each one of them spans nb_clusters and has two copy-on-write regions located immediately before and after the middle region touched by that part of the write request. Even when those regions themselves are empty their offsets must be correct because they are used to know the location of the middle region. This was not always the case but it is not a problem anymore because the only two places where QCowL2Meta structures are created (calculate_l2_meta() and qcow2_co_truncate()) ensure that the copy-on-write regions are correctly defined, and so do assertions like the ones in perform_cow(). The conditional initialization of the 'written_to' variable is therefore unnecessary and is removed by this patch. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20201007161323.4667-1-berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-10-02qcow2: Use L1E_SIZE in qcow2_write_l1_entry()Alberto Garcia
We overlooked these in 02b1ecfa100e7ecc2306560cd27a4a2622bfeb04 Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <20200928162333.14998-1-berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-09-15qcow2: Convert qcow2_alloc_cluster_offset() into qcow2_alloc_host_offset()Alberto Garcia
qcow2_alloc_cluster_offset() takes an (unaligned) guest offset and returns the (aligned) offset of the corresponding cluster in the qcow2 image. In practice none of the callers need to know where the cluster starts so this patch makes the function calculate and return the final host offset directly. The function is also renamed accordingly. See 388e581615 for a similar change to qcow2_get_cluster_offset(). Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <9bfef50ec9200d752413be4fc2aeb22a28378817.1599833007.git.berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-09-15qcow2: Make qcow2_free_any_clusters() free only one clusterAlberto Garcia
This function takes an L2 entry and a number of clusters to free. Although in principle it can free any type of cluster (using the L2 entry to determine its type) in practice the API is broken because compressed clusters have a variable size and there is no way to free more than one without having the L2 entry of each one of them. The good news all callers are passing nb_clusters=1 so we can simply get rid of that parameter. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <77cea0f4616f921d37e971b3c5b18a2faa24b173.1599573989.git.berto@igalia.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-09-15qcow2: Rewrite the documentation of qcow2_alloc_cluster_offset()Alberto Garcia
The current text corresponds to an earlier, simpler version of this function and it does not explain how it works now. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <bb5bd06f07c5a05b0818611de0d06ec5b66c8df3.1599150873.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-09-15qcow2: Fix removal of list members from BDRVQcow2State.cluster_allocsAlberto Garcia
When a write request needs to allocate new clusters (or change the L2 bitmap of existing ones) a QCowL2Meta structure is created so the L2 metadata can be later updated and any copy-on-write can be performed if necessary. A write request can span a region consisting of an arbitrary combination of previously unallocated and allocated clusters, and if the unallocated ones can be put contiguous to the existing ones then QEMU will do so in order to minimize the number of write operations. In practice this means that a write request has not just one but a number of QCowL2Meta structures. All of them are added to the cluster_allocs list that is stored in BDRVQcow2State and is used to detect overlapping requests. After the write request finishes all its associated QCowL2Meta are removed from that list. calculate_l2_meta() takes care of creating and putting those structures in the list, and qcow2_handle_l2meta() takes care of removing them. The problem is that the error path in handle_alloc() also tries to remove an item in that list, a remnant from the time when this was handled there (that code would not even be correct anymore because it only removes one struct and not all the ones from the same write request). This can trigger a double removal of the same item from the list, causing a crash. This is not easy to reproduce in practice because it requires that do_alloc_cluster_offset() fails after a successful previous allocation during the same write request, but it can be reproduced with the included test case. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <3440a1c4d53c4fe48312b478c96accb338cbef7c.1599150873.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-09-15qcow2: Use macros for the L1, refcount and bitmap table entry sizesAlberto Garcia
This patch replaces instances of sizeof(uint64_t) in the qcow2 driver with macros that indicate what those sizes are actually referring to. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <20200828110828.13833-1-berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-09-10block/qcow2-cluster: Add missing "fallthrough" annotationThomas Huth
When compiling with -Werror=implicit-fallthrough, the compiler currently complains: ../../devel/qemu/block/qcow2-cluster.c: In function ‘cluster_needs_new_alloc’: ../../devel/qemu/block/qcow2-cluster.c:1320:12: error: this statement may fall through [-Werror=implicit-fallthrough=] if (l2_entry & QCOW_OFLAG_COPIED) { ^ ../../devel/qemu/block/qcow2-cluster.c:1323:5: note: here case QCOW2_CLUSTER_UNALLOCATED: ^~~~ It's quite obvious that the fallthrough is intended here, so let's add a comment to silence the compiler warning. Signed-off-by: Thomas Huth <thuth@redhat.com> Message-Id: <20200908070028.193298-1-thuth@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-08-25qcow2: Assert that expand_zero_clusters_in_l1() does not support subclustersAlberto Garcia
This function is only used by qcow2_expand_zero_clusters() to downgrade a qcow2 image to a previous version. This would require transforming all extended L2 entries into normal L2 entries but this is not a simple task and there are no plans to implement this at the moment. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <15e65112b4144381b4d8c0bdf8fb76b0d813e3d1.1594396418.git.berto@igalia.com> [mreitz: Fixed comment style] Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add prealloc field to QCowL2MetaAlberto Garcia
This field allows us to indicate that the L2 metadata update does not come from a write request with actual data but from a preallocation request. For traditional images this does not make any difference, but for images with extended L2 entries this means that the clusters are allocated normally in the L2 table but individual subclusters are marked as unallocated. This will allow preallocating images that have a backing file. There is one special case: when we resize an existing image we can also request that the new clusters are preallocated. If the image already had a backing file then we have to hide any possible stale data and zero out the new clusters (see commit 955c7d6687 for more details). In this case the subclusters cannot be left as unallocated so the L2 bitmap must be updated. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <960d4c444a4f5a870e2b47e5da322a73cd9a2f5a.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add subcluster support to qcow2_co_pwrite_zeroes()Alberto Garcia
This works now at the subcluster level and pwrite_zeroes_alignment is updated accordingly. qcow2_cluster_zeroize() is turned into qcow2_subcluster_zeroize() with the following changes: - The request can now be subcluster-aligned. - The cluster-aligned body of the request is still zeroized using zero_in_l2_slice() as before. - The subcluster-aligned head and tail of the request are zeroized with the new zero_l2_subclusters() function. There is just one thing to take into account for a possible future improvement: compressed clusters cannot be partially zeroized so zero_l2_subclusters() on the head or the tail can return -ENOTSUP. This makes the caller repeat the *complete* request and write actual zeroes to disk. This is sub-optimal because 1) if the head area was compressed we would still be able to use the fast path for the body and possibly the tail. 2) if the tail area was compressed we are writing zeroes to the head and the body areas, which are already zeroized. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <17e05e2ee7e12f10dcf012da81e83ebe27eb3bef.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Clear the L2 bitmap when allocating a compressed clusterAlberto Garcia
Compressed clusters always have the bitmap part of the extended L2 entry set to 0. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <04455b3de5dfeb9d1cfe1fc7b02d7060a6e09710.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2()Alberto Garcia
The L2 bitmap needs to be updated after each write to indicate what new subclusters are now allocated. This needs to happen even if the cluster was already allocated and the L2 entry was otherwise valid. In some cases however a write operation doesn't need change the L2 bitmap (because all affected subclusters were already allocated). This is detected in calculate_l2_meta(), and qcow2_alloc_cluster_link_l2() is never called in those cases. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <0875620d49f44320334b6a91c73b3f301f975f38.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add subcluster support to discard_in_l2_slice()Alberto Garcia
Two things need to be taken into account here: 1) With full_discard == true the L2 entry must be cleared completely. This also includes the L2 bitmap if the image has extended L2 entries. 2) With full_discard == false we have to make the discarded cluster read back as zeroes. With normal L2 entries this is done with the QCOW_OFLAG_ZERO bit, whereas with extended L2 entries this is done with the individual 'all zeroes' bits for each subcluster. Note however that QCOW_OFLAG_ZERO is not supported in v2 qcow2 images so, if there is a backing file, discard cannot guarantee that the image will read back as zeroes. If this is important for the caller it should forbid it as qcow2_co_pdiscard() does (see 80f5c01183 for more details). Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <5ef8274e628aa3ab559bfac467abf488534f2b76.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add subcluster support to zero_in_l2_slice()Alberto Garcia
The QCOW_OFLAG_ZERO bit that indicates that a cluster reads as zeroes is only used in standard L2 entries. Extended L2 entries use individual 'all zeroes' bits for each subcluster. This must be taken into account when updating the L2 entry and also when deciding that an existing entry does not need to be updated. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <b61d61606d8c9b367bd641ab37351ddb9172799a.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add subcluster support to qcow2_get_host_offset()Alberto Garcia
The logic of this function remains pretty much the same, except that it uses count_contiguous_subclusters(), which combines the logic of count_contiguous_clusters() / count_contiguous_clusters_unallocated() and checks individual subclusters. qcow2_cluster_to_subcluster_type() is not necessary as a separate function anymore so it's inlined into its caller. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <d2193fd48653a350d80f0eca1c67b1d9053fb2f3.1594396418.git.berto@igalia.com> [mreitz: Initialize expected_type to anything] Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add subcluster support to calculate_l2_meta()Alberto Garcia
If an image has subclusters then there are more copy-on-write scenarios that we need to consider. Let's say we have a write request from the middle of subcluster #3 until the end of the cluster: 1) If we are writing to a newly allocated cluster then we need copy-on-write. The previous contents of subclusters #0 to #3 must be copied to the new cluster. We can optimize this process by skipping all leading unallocated or zero subclusters (the status of those skipped subclusters will be reflected in the new L2 bitmap). 2) If we are overwriting an existing cluster: 2.1) If subcluster #3 is unallocated or has the all-zeroes bit set then we need copy-on-write (on subcluster #3 only). 2.2) If subcluster #3 was already allocated then there is no need for any copy-on-write. However we still need to update the L2 bitmap to reflect possible changes in the allocation status of subclusters #4 to #31. Because of this, this function checks if all the overwritten subclusters are already allocated and in this case it returns without creating a new QCowL2Meta structure. After all these changes l2meta_cow_start() and l2meta_cow_end() are not necessarily cluster-aligned anymore. We need to update the calculation of old_start and old_end in handle_dependencies() to guarantee that no two requests try to write on the same cluster. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <4292dd56e4446d386a2fe307311737a711c00708.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Replace QCOW2_CLUSTER_* with QCOW2_SUBCLUSTER_*Alberto Garcia
In order to support extended L2 entries some functions of the qcow2 driver need to start dealing with subclusters instead of clusters. qcow2_get_host_offset() is modified to return the subcluster type instead of the cluster type, and all callers are updated to replace all values of QCow2ClusterType with their QCow2SubclusterType equivalents. This patch only changes the data types, there are no semantic changes. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <f6c29737c295f32cbee74c903c30b01820363b34.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add cluster type parameter to qcow2_get_host_offset()Alberto Garcia
This function returns an integer that can be either an error code or a cluster type (a value from the QCow2ClusterType enum). We are going to start using subcluster types instead of cluster types in some functions so it's better to use the exact data types instead of integers for clarity and in order to detect errors more easily. This patch makes qcow2_get_host_offset() return 0 on success and puts the returned cluster type in a separate parameter. There are no semantic changes. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <396b6eab1859a271551dcd7dcba77f8934aa3c3f.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add qcow2_get_subcluster_range_type()Alberto Garcia
There are situations in which we want to know how many contiguous subclusters of the same type there are in a given cluster. This can be done by simply iterating over the subclusters and repeatedly calling qcow2_get_subcluster_type() for each one of them. However once we determined the type of a subcluster we can check the rest efficiently by counting the number of adjacent ones (or zeroes) in the bitmap. This is what this function does. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <db917263d568ec6ffb4a41cac3c9100f96bf6c18.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add l2_entry_size()Alberto Garcia
qcow2 images with subclusters have 128-bit L2 entries. The first 64 bits contain the same information as traditional images and the last 64 bits form a bitmap with the status of each individual subcluster. Because of that we cannot assume that L2 entries are sizeof(uint64_t) anymore. This function returns the proper value for the image. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <d34d578bd0380e739e2dde3e8dd6187d3d249fa9.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add get_l2_entry() and set_l2_entry()Alberto Garcia
The size of an L2 entry is 64 bits, but if we want to have subclusters we need extended L2 entries. This means that we have to access L2 tables and slices differently depending on whether an image has extended L2 entries or not. This patch replaces all l2_slice[] accesses with calls to get_l2_entry() and set_l2_entry(). Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <9586363531fec125ba1386e561762d3e4224e9fc.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Process QCOW2_CLUSTER_ZERO_ALLOC clusters in handle_copied()Alberto Garcia
When writing to a qcow2 file there are two functions that take a virtual offset and return a host offset, possibly allocating new clusters if necessary: - handle_copied() looks for normal data clusters that are already allocated and have a reference count of 1. In those clusters we can simply write the data and there is no need to perform any copy-on-write. - handle_alloc() looks for clusters that do need copy-on-write, either because they haven't been allocated yet, because their reference count is != 1 or because they are ZERO_ALLOC clusters. The ZERO_ALLOC case is a bit special because those are clusters that are already allocated and they could perfectly be dealt with in handle_copied() (as long as copy-on-write is performed when required). In fact, there is extra code specifically for them in handle_alloc() that tries to reuse the existing allocation if possible and frees them otherwise. This patch changes the handling of ZERO_ALLOC clusters so the semantics of these two functions are now like this: - handle_copied() looks for clusters that are already allocated and which we can overwrite (NORMAL and ZERO_ALLOC clusters with a reference count of 1). - handle_alloc() looks for clusters for which we need a new allocation (all other cases). One important difference after this change is that clusters found in handle_copied() may now require copy-on-write, but this will be necessary anyway once we add support for subclusters. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <eb17fc938f6be7be2e8d8ff42763d2c19241f866.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Split cluster_needs_cow() out of count_cow_clusters()Alberto Garcia
We are going to need it in other places. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <65e5d9627ca2ebe7e62deaeddf60949c33067d9d.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Add calculate_l2_meta()Alberto Garcia
handle_alloc() creates a QCowL2Meta structure in order to update the image metadata and perform the necessary copy-on-write operations. This patch moves that code to a separate function so it can be used from other places. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <e5bc4a648dac31972bfa7a0e554be8064be78799.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-25qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset()Alberto Garcia
qcow2_get_cluster_offset() takes an (unaligned) guest offset and returns the (aligned) offset of the corresponding cluster in the qcow2 image. In practice none of the callers need to know where the cluster starts so this patch makes the function calculate and return the final host offset directly. The function is also renamed accordingly. There is a pre-existing exception with compressed clusters: in this case the function returns the complete cluster descriptor (containing the offset and size of the compressed data). This does not change with this patch but it is now documented. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <ffae6cdc5ca8950e8280ac0f696dcc376cb07095.1594396418.git.berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2020-08-05qcow2-cluster: Fix integer left shift error in qcow2_alloc_cluster_link_l2()Tuguoyi
When calculating the offset, the result of left shift operation will be promoted to type int64 automatically because the left operand of + operator is uint64_t. but the result after integer promotion may be produce an error value for us and trigger the following asserting error. For example, consider i=0x2000, cluster_bits=18, the result of left shift operation will be 0x80000000. Cause argument i is of signed integer type, the result is automatically promoted to 0xffffffff80000000 which is not we expected The way to trigger the assertion error: qemu-img create -f qcow2 -o preallocation=full,cluster_size=256k tmpdisk 10G This patch fix it by casting @i to uint64_t before doing left shift operation Signed-off-by: Guoyi Tu <tu.guoyi@h3c.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Message-id: 81ba90fe0c014f269621c283269b42ad@h3c.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
generated by cgit v1.2.3 (git 2.26.2) at 2024-12-03 21:53:19 +0000