<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/fs/btrfs/inode.c, branch v6.7</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>Merge tag 'for-6.7-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux</title>
<updated>2023-12-14T19:53:00+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-12-14T19:53:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=bdb2701f0b6822d711ec34968ccef70b73a91da7'/>
<id>bdb2701f0b6822d711ec34968ccef70b73a91da7</id>
<content type='text'>
Pull btrfs fixes from David Sterba:
  "Some fixes to quota accounting code, mostly around error handling and
   correctness:

   - free reserves on various error paths, after IO errors or
     transaction abort

   - don't clear reserved range at the folio release time, it'll be
     properly cleared after final write

   - fix integer overflow due to int used when passing around size of
     freed reservations

   - fix a regression in squota accounting that missed some cases with
     delayed refs"

* tag 'for-6.7-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: ensure releasing squota reserve on head refs
  btrfs: don't clear qgroup reserved bit in release_folio
  btrfs: free qgroup pertrans reserve on transaction abort
  btrfs: fix qgroup_free_reserved_data int overflow
  btrfs: free qgroup reserve when ORDERED_IOERR is set
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull btrfs fixes from David Sterba:
  "Some fixes to quota accounting code, mostly around error handling and
   correctness:

   - free reserves on various error paths, after IO errors or
     transaction abort

   - don't clear reserved range at the folio release time, it'll be
     properly cleared after final write

   - fix integer overflow due to int used when passing around size of
     freed reservations

   - fix a regression in squota accounting that missed some cases with
     delayed refs"

* tag 'for-6.7-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: ensure releasing squota reserve on head refs
  btrfs: don't clear qgroup reserved bit in release_folio
  btrfs: free qgroup pertrans reserve on transaction abort
  btrfs: fix qgroup_free_reserved_data int overflow
  btrfs: free qgroup reserve when ORDERED_IOERR is set
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: fix qgroup_free_reserved_data int overflow</title>
<updated>2023-12-06T21:32:46+00:00</updated>
<author>
<name>Boris Burkov</name>
<email>boris@bur.io</email>
</author>
<published>2023-12-01T21:00:10+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9e65bfca24cf1d77e4a5c7a170db5867377b3fe7'/>
<id>9e65bfca24cf1d77e4a5c7a170db5867377b3fe7</id>
<content type='text'>
The reserved data counter and input parameter is a u64, but we
inadvertently accumulate it in an int. Overflowing that int results in
freeing the wrong amount of data and breaking reserve accounting.

Unfortunately, this overflow rot spreads from there, as the qgroup
release/free functions rely on returning an int to take advantage of
negative values for error codes.

Therefore, the full fix is to return the "released" or "freed" amount by
a u64 argument and to return 0 or negative error code via the return
value.

Most of the call sites simply ignore the return value, though some
of them handle the error and count the returned bytes. Change all of
them accordingly.

CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Qu Wenruo &lt;wqu@suse.com&gt;
Signed-off-by: Boris Burkov &lt;boris@bur.io&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The reserved data counter and input parameter is a u64, but we
inadvertently accumulate it in an int. Overflowing that int results in
freeing the wrong amount of data and breaking reserve accounting.

Unfortunately, this overflow rot spreads from there, as the qgroup
release/free functions rely on returning an int to take advantage of
negative values for error codes.

Therefore, the full fix is to return the "released" or "freed" amount by
a u64 argument and to return 0 or negative error code via the return
value.

Most of the call sites simply ignore the return value, though some
of them handle the error and count the returned bytes. Change all of
them accordingly.

CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Qu Wenruo &lt;wqu@suse.com&gt;
Signed-off-by: Boris Burkov &lt;boris@bur.io&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'for-6.7-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux</title>
<updated>2023-11-13T17:09:12+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-11-13T17:09:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9bacdd8996c77c42ca004440be610692275ff9d0'/>
<id>9bacdd8996c77c42ca004440be610692275ff9d0</id>
<content type='text'>
Pull btrfs fixes from David Sterba:

 - fix potential overflow in returned value from SEARCH_TREE_V2
   ioctl on 32bit architecture

 - zoned mode fixes:

     - drop unnecessary write pointer check for RAID0/RAID1/RAID10
       profiles, now it works because of raid-stripe-tree

     - wait for finishing the zone when direct IO needs a new
       allocation

 - simple quota fixes:

     - pass correct owning root pointer when cleaning up an
       aborted transaction

     - fix leaking some structures when processing delayed refs

     - change key type number of BTRFS_EXTENT_OWNER_REF_KEY,
       reorder it before inline refs that are supposed to be
       sorted, keeping the original number would complicate a lot
       of things; this change needs an updated version of
       btrfs-progs to work and filesystems need to be recreated

 - fix error pointer dereference after failure to allocate fs
   devices

 - fix race between accounting qgroup extents and removing a
   qgroup

* tag 'for-6.7-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: make OWNER_REF_KEY type value smallest among inline refs
  btrfs: fix qgroup record leaks when using simple quotas
  btrfs: fix race between accounting qgroup extents and removing a qgroup
  btrfs: fix error pointer dereference after failure to allocate fs devices
  btrfs: make found_logical_ret parameter mandatory for function queue_scrub_stripe()
  btrfs: get correct owning_root when dropping snapshot
  btrfs: zoned: wait for data BG to be finished on direct IO allocation
  btrfs: zoned: drop no longer valid write pointer check
  btrfs: directly return 0 on no error code in btrfs_insert_raid_extent()
  btrfs: use u64 for buffer sizes in the tree search ioctls
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull btrfs fixes from David Sterba:

 - fix potential overflow in returned value from SEARCH_TREE_V2
   ioctl on 32bit architecture

 - zoned mode fixes:

     - drop unnecessary write pointer check for RAID0/RAID1/RAID10
       profiles, now it works because of raid-stripe-tree

     - wait for finishing the zone when direct IO needs a new
       allocation

 - simple quota fixes:

     - pass correct owning root pointer when cleaning up an
       aborted transaction

     - fix leaking some structures when processing delayed refs

     - change key type number of BTRFS_EXTENT_OWNER_REF_KEY,
       reorder it before inline refs that are supposed to be
       sorted, keeping the original number would complicate a lot
       of things; this change needs an updated version of
       btrfs-progs to work and filesystems need to be recreated

 - fix error pointer dereference after failure to allocate fs
   devices

 - fix race between accounting qgroup extents and removing a
   qgroup

* tag 'for-6.7-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: make OWNER_REF_KEY type value smallest among inline refs
  btrfs: fix qgroup record leaks when using simple quotas
  btrfs: fix race between accounting qgroup extents and removing a qgroup
  btrfs: fix error pointer dereference after failure to allocate fs devices
  btrfs: make found_logical_ret parameter mandatory for function queue_scrub_stripe()
  btrfs: get correct owning_root when dropping snapshot
  btrfs: zoned: wait for data BG to be finished on direct IO allocation
  btrfs: zoned: drop no longer valid write pointer check
  btrfs: directly return 0 on no error code in btrfs_insert_raid_extent()
  btrfs: use u64 for buffer sizes in the tree search ioctls
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: zoned: wait for data BG to be finished on direct IO allocation</title>
<updated>2023-11-03T15:39:01+00:00</updated>
<author>
<name>Naohiro Aota</name>
<email>naohiro.aota@wdc.com</email>
</author>
<published>2023-10-17T08:00:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=776a838f1fa95670c1c1cf7109a898090b473fa3'/>
<id>776a838f1fa95670c1c1cf7109a898090b473fa3</id>
<content type='text'>
Running the fio command below on a ZNS device results in "Resource
temporarily unavailable" error.

  $ sudo fio --name=w --directory=/mnt --filesize=1GB --bs=16MB --numjobs=16 \
        --rw=write --ioengine=libaio --iodepth=128 --direct=1

  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=117440512, buflen=16777216
  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=134217728, buflen=16777216
  ...

This happens because -EAGAIN error returned from btrfs_reserve_extent()
called from btrfs_new_extent_direct() is spilling over to the userland.

btrfs_reserve_extent() returns -EAGAIN when there is no active zone
available. Then, the caller should wait for some other on-going IO to
finish a zone and retry the allocation.

This logic is already implemented for buffered write in cow_file_range(),
but it is missing for the direct IO counterpart. Implement the same logic
for it.

Reported-by: Shinichiro Kawasaki &lt;shinichiro.kawasaki@wdc.com&gt;
Fixes: 2ce543f47843 ("btrfs: zoned: wait until zone is finished when allocation didn't progress")
CC: stable@vger.kernel.org # 6.1+
Tested-by: Shinichiro Kawasaki &lt;shinichiro.kawasaki@wdc.com&gt;
Reviewed-by: Johannes Thumshirn &lt;johannes.thumshirn@wdc.com&gt;
Signed-off-by: Naohiro Aota &lt;naohiro.aota@wdc.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Running the fio command below on a ZNS device results in "Resource
temporarily unavailable" error.

  $ sudo fio --name=w --directory=/mnt --filesize=1GB --bs=16MB --numjobs=16 \
        --rw=write --ioengine=libaio --iodepth=128 --direct=1

  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=117440512, buflen=16777216
  fio: io_u error on file /mnt/w.2.0: Resource temporarily unavailable: write offset=134217728, buflen=16777216
  ...

This happens because -EAGAIN error returned from btrfs_reserve_extent()
called from btrfs_new_extent_direct() is spilling over to the userland.

btrfs_reserve_extent() returns -EAGAIN when there is no active zone
available. Then, the caller should wait for some other on-going IO to
finish a zone and retry the allocation.

This logic is already implemented for buffered write in cow_file_range(),
but it is missing for the direct IO counterpart. Implement the same logic
for it.

Reported-by: Shinichiro Kawasaki &lt;shinichiro.kawasaki@wdc.com&gt;
Fixes: 2ce543f47843 ("btrfs: zoned: wait until zone is finished when allocation didn't progress")
CC: stable@vger.kernel.org # 6.1+
Tested-by: Shinichiro Kawasaki &lt;shinichiro.kawasaki@wdc.com&gt;
Reviewed-by: Johannes Thumshirn &lt;johannes.thumshirn@wdc.com&gt;
Signed-off-by: Naohiro Aota &lt;naohiro.aota@wdc.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'for-6.7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux</title>
<updated>2023-10-30T20:42:06+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2023-10-30T20:42:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d5acbc60fafbe0fc94c552ce916dd592cd4c6371'/>
<id>d5acbc60fafbe0fc94c552ce916dd592cd4c6371</id>
<content type='text'>
Pull btrfs updates from David Sterba:
 "New features:

   - raid-stripe-tree

     New tree for logical file extent mapping where the physical mapping
     may not match on multiple devices. This is now used in zoned mode
     to implement RAID0/RAID1* profiles, but can be used in non-zoned
     mode as well. The support for RAID56 is in development and will
     eventually fix the problems with the current implementation. This
     is a backward incompatible feature and has to be enabled at mkfs
     time.

   - simple quota accounting (squota)

     A simplified mode of qgroup that accounts all space on the initial
     extent owners (a subvolume), the snapshots are then cheap to create
     and delete. The deletion of snapshots in fully accounting qgroups
     is a known CPU/IO performance bottleneck.

     The squota is not suitable for the general use case but works well
     for containers where the original subvolume exists for the whole
     time. This is a backward incompatible feature as it needs extending
     some structures, but can be enabled on an existing filesystem.

   - temporary filesystem fsid (temp_fsid)

     The fsid identifies a filesystem and is hard coded in the
     structures, which disallows mounting the same fsid found on
     different devices.

     For a single device filesystem this is not strictly necessary, a
     new temporary fsid can be generated on mount e.g. after a device is
     cloned. This will be used by Steam Deck for root partition A/B
     testing, or can be used for VM root images.

  Other user visible changes:

   - filesystems with partially finished metadata_uuid conversion cannot
     be mounted anymore and the uuid fixup has to be done by btrfs-progs
     (btrfstune).

  Performance improvements:

   - reduce reservations for checksum deletions (with enabled free space
     tree by factor of 4), on a sample workload on file with many
     extents the deletion time decreased by 12%

   - make extent state merges more efficient during insertions, reduce
     rb-tree iterations (run time of critical functions reduced by 5%)

  Core changes:

   - the integrity check functionality has been removed, this was a
     debugging feature and removal does not affect other integrity
     checks like checksums or tree-checker

   - space reservation changes:

      - more efficient delayed ref reservations, this avoids building up
        too much work or overusing or exhausting the global block
        reserve in some situations

      - move delayed refs reservation to the transaction start time,
        this prevents some ENOSPC corner cases related to exhaustion of
        global reserve

      - improvements in reducing excessive reservations for block group
        items

      - adjust overcommit logic in near full situations, account for one
        more chunk to eventually allocate metadata chunk, this is mostly
        relevant for small filesystems (&lt;10GiB)

   - single device filesystems are scanned but not registered (except
     seed devices), this allows temp_fsid to work

   - qgroup iterations do not need GFP_ATOMIC allocations anymore

   - cleanups, refactoring, reduced data structure size, function
     parameter simplifications, error handling fixes"

* tag 'for-6.7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (156 commits)
  btrfs: open code timespec64 in struct btrfs_inode
  btrfs: remove redundant log root tree index assignment during log sync
  btrfs: remove redundant initialization of variable dirty in btrfs_update_time()
  btrfs: sysfs: show temp_fsid feature
  btrfs: disable the device add feature for temp-fsid
  btrfs: disable the seed feature for temp-fsid
  btrfs: update comment for temp-fsid, fsid, and metadata_uuid
  btrfs: remove pointless empty log context list check when syncing log
  btrfs: update comment for struct btrfs_inode::lock
  btrfs: remove pointless barrier from btrfs_sync_file()
  btrfs: add and use helpers for reading and writing last_trans_committed
  btrfs: add and use helpers for reading and writing fs_info-&gt;generation
  btrfs: add and use helpers for reading and writing log_transid
  btrfs: add and use helpers for reading and writing last_log_commit
  btrfs: support cloned-device mount capability
  btrfs: add helper function find_fsid_by_disk
  btrfs: stop reserving excessive space for block group item insertions
  btrfs: stop reserving excessive space for block group item updates
  btrfs: reorder btrfs_inode to fill gaps
  btrfs: open code btrfs_ordered_inode_tree in btrfs_inode
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull btrfs updates from David Sterba:
 "New features:

   - raid-stripe-tree

     New tree for logical file extent mapping where the physical mapping
     may not match on multiple devices. This is now used in zoned mode
     to implement RAID0/RAID1* profiles, but can be used in non-zoned
     mode as well. The support for RAID56 is in development and will
     eventually fix the problems with the current implementation. This
     is a backward incompatible feature and has to be enabled at mkfs
     time.

   - simple quota accounting (squota)

     A simplified mode of qgroup that accounts all space on the initial
     extent owners (a subvolume), the snapshots are then cheap to create
     and delete. The deletion of snapshots in fully accounting qgroups
     is a known CPU/IO performance bottleneck.

     The squota is not suitable for the general use case but works well
     for containers where the original subvolume exists for the whole
     time. This is a backward incompatible feature as it needs extending
     some structures, but can be enabled on an existing filesystem.

   - temporary filesystem fsid (temp_fsid)

     The fsid identifies a filesystem and is hard coded in the
     structures, which disallows mounting the same fsid found on
     different devices.

     For a single device filesystem this is not strictly necessary, a
     new temporary fsid can be generated on mount e.g. after a device is
     cloned. This will be used by Steam Deck for root partition A/B
     testing, or can be used for VM root images.

  Other user visible changes:

   - filesystems with partially finished metadata_uuid conversion cannot
     be mounted anymore and the uuid fixup has to be done by btrfs-progs
     (btrfstune).

  Performance improvements:

   - reduce reservations for checksum deletions (with enabled free space
     tree by factor of 4), on a sample workload on file with many
     extents the deletion time decreased by 12%

   - make extent state merges more efficient during insertions, reduce
     rb-tree iterations (run time of critical functions reduced by 5%)

  Core changes:

   - the integrity check functionality has been removed, this was a
     debugging feature and removal does not affect other integrity
     checks like checksums or tree-checker

   - space reservation changes:

      - more efficient delayed ref reservations, this avoids building up
        too much work or overusing or exhausting the global block
        reserve in some situations

      - move delayed refs reservation to the transaction start time,
        this prevents some ENOSPC corner cases related to exhaustion of
        global reserve

      - improvements in reducing excessive reservations for block group
        items

      - adjust overcommit logic in near full situations, account for one
        more chunk to eventually allocate metadata chunk, this is mostly
        relevant for small filesystems (&lt;10GiB)

   - single device filesystems are scanned but not registered (except
     seed devices), this allows temp_fsid to work

   - qgroup iterations do not need GFP_ATOMIC allocations anymore

   - cleanups, refactoring, reduced data structure size, function
     parameter simplifications, error handling fixes"

* tag 'for-6.7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (156 commits)
  btrfs: open code timespec64 in struct btrfs_inode
  btrfs: remove redundant log root tree index assignment during log sync
  btrfs: remove redundant initialization of variable dirty in btrfs_update_time()
  btrfs: sysfs: show temp_fsid feature
  btrfs: disable the device add feature for temp-fsid
  btrfs: disable the seed feature for temp-fsid
  btrfs: update comment for temp-fsid, fsid, and metadata_uuid
  btrfs: remove pointless empty log context list check when syncing log
  btrfs: update comment for struct btrfs_inode::lock
  btrfs: remove pointless barrier from btrfs_sync_file()
  btrfs: add and use helpers for reading and writing last_trans_committed
  btrfs: add and use helpers for reading and writing fs_info-&gt;generation
  btrfs: add and use helpers for reading and writing log_transid
  btrfs: add and use helpers for reading and writing last_log_commit
  btrfs: support cloned-device mount capability
  btrfs: add helper function find_fsid_by_disk
  btrfs: stop reserving excessive space for block group item insertions
  btrfs: stop reserving excessive space for block group item updates
  btrfs: reorder btrfs_inode to fill gaps
  btrfs: open code btrfs_ordered_inode_tree in btrfs_inode
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: convert to new timestamp accessors</title>
<updated>2023-10-18T11:26:19+00:00</updated>
<author>
<name>Jeff Layton</name>
<email>jlayton@kernel.org</email>
</author>
<published>2023-10-04T18:52:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=b1c38a1338c90597c7af66985a9e31152ae8cfd3'/>
<id>b1c38a1338c90597c7af66985a9e31152ae8cfd3</id>
<content type='text'>
Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton &lt;jlayton@kernel.org&gt;
Link: https://lore.kernel.org/r/20231004185347.80880-21-jlayton@kernel.org
Signed-off-by: Christian Brauner &lt;brauner@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton &lt;jlayton@kernel.org&gt;
Link: https://lore.kernel.org/r/20231004185347.80880-21-jlayton@kernel.org
Signed-off-by: Christian Brauner &lt;brauner@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: open code timespec64 in struct btrfs_inode</title>
<updated>2023-10-12T14:44:19+00:00</updated>
<author>
<name>David Sterba</name>
<email>dsterba@suse.com</email>
</author>
<published>2023-09-29T19:18:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=c6e8f898f56fae2cb5bc4396bec480f23cd8b066'/>
<id>c6e8f898f56fae2cb5bc4396bec480f23cd8b066</id>
<content type='text'>
The type of timespec64::tv_nsec is 'unsigned long', while we have only
u32 for on-disk and in-memory. This wastes a few bytes in btrfs_inode.
Add separate members for sec and nsec with the corresponding type width.
This creates a 4 byte hole in btrfs_inode which can be utilized in the
future.

Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The type of timespec64::tv_nsec is 'unsigned long', while we have only
u32 for on-disk and in-memory. This wastes a few bytes in btrfs_inode.
Add separate members for sec and nsec with the corresponding type width.
This creates a 4 byte hole in btrfs_inode which can be utilized in the
future.

Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: remove redundant initialization of variable dirty in btrfs_update_time()</title>
<updated>2023-10-12T14:44:19+00:00</updated>
<author>
<name>Colin Ian King</name>
<email>colin.i.king@gmail.com</email>
</author>
<published>2023-08-18T13:55:25+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a666ce9babf2e3ade3809163ccc81d5805bb503b'/>
<id>a666ce9babf2e3ade3809163ccc81d5805bb503b</id>
<content type='text'>
The variable dirty is initialized with a value that is never read, it
is being re-assigned later on. Remove the redundant initialization.
Cleans up clang scan build warning:

  fs/btrfs/inode.c:5965:7: warning: Value stored to 'dirty' during its
  initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King &lt;colin.i.king@gmail.com&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The variable dirty is initialized with a value that is never read, it
is being re-assigned later on. Remove the redundant initialization.
Cleans up clang scan build warning:

  fs/btrfs/inode.c:5965:7: warning: Value stored to 'dirty' during its
  initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King &lt;colin.i.king@gmail.com&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: add and use helpers for reading and writing fs_info-&gt;generation</title>
<updated>2023-10-12T14:44:17+00:00</updated>
<author>
<name>Filipe Manana</name>
<email>fdmanana@suse.com</email>
</author>
<published>2023-10-04T10:38:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=4a4f8fe2b0230c22aba40c9f8ea7b9c6fcfc8417'/>
<id>4a4f8fe2b0230c22aba40c9f8ea7b9c6fcfc8417</id>
<content type='text'>
Currently the generation field of struct btrfs_fs_info is always modified
while holding fs_info-&gt;trans_lock locked. Most readers will access this
field without taking that lock but while holding a transaction handle,
which is safe to do due to the transaction life cycle.

However there are other readers that are neither holding the lock nor
holding a transaction handle open:

1) When reading an inode from disk, at btrfs_read_locked_inode();

2) When reading the generation to expose it to sysfs, at
   btrfs_generation_show();

3) Early in the fsync path, at skip_inode_logging();

4) When creating a hole at btrfs_cont_expand(), during write paths,
   truncate and reflinking;

5) In the fs_info ioctl (btrfs_ioctl_fs_info());

6) While mounting the filesystem, in the open_ctree() path. In these
   cases it's safe to directly read fs_info-&gt;generation as no one
   can concurrently start a transaction and update fs_info-&gt;generation.

In case of the fsync path, races here should be harmless, and in the worst
case they may cause a fsync to log an inode when it's not really needed,
so nothing bad from a functional perspective. In the other cases it's not
so clear if functional problems may arise, though in case 1 rare things
like a load/store tearing [1] may cause the BTRFS_INODE_NEEDS_FULL_SYNC
flag not being set on an inode and therefore result in incorrect logging
later on in case a fsync call is made.

To avoid data race warnings from tools like KCSAN and other issues such
as load and store tearing (amongst others, see [1]), create helpers to
access the generation field of struct btrfs_fs_info using READ_ONCE() and
WRITE_ONCE(), and use these helpers where needed.

[1] https://lwn.net/Articles/793253/

Signed-off-by: Filipe Manana &lt;fdmanana@suse.com&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Currently the generation field of struct btrfs_fs_info is always modified
while holding fs_info-&gt;trans_lock locked. Most readers will access this
field without taking that lock but while holding a transaction handle,
which is safe to do due to the transaction life cycle.

However there are other readers that are neither holding the lock nor
holding a transaction handle open:

1) When reading an inode from disk, at btrfs_read_locked_inode();

2) When reading the generation to expose it to sysfs, at
   btrfs_generation_show();

3) Early in the fsync path, at skip_inode_logging();

4) When creating a hole at btrfs_cont_expand(), during write paths,
   truncate and reflinking;

5) In the fs_info ioctl (btrfs_ioctl_fs_info());

6) While mounting the filesystem, in the open_ctree() path. In these
   cases it's safe to directly read fs_info-&gt;generation as no one
   can concurrently start a transaction and update fs_info-&gt;generation.

In case of the fsync path, races here should be harmless, and in the worst
case they may cause a fsync to log an inode when it's not really needed,
so nothing bad from a functional perspective. In the other cases it's not
so clear if functional problems may arise, though in case 1 rare things
like a load/store tearing [1] may cause the BTRFS_INODE_NEEDS_FULL_SYNC
flag not being set on an inode and therefore result in incorrect logging
later on in case a fsync call is made.

To avoid data race warnings from tools like KCSAN and other issues such
as load and store tearing (amongst others, see [1]), create helpers to
access the generation field of struct btrfs_fs_info using READ_ONCE() and
WRITE_ONCE(), and use these helpers where needed.

[1] https://lwn.net/Articles/793253/

Signed-off-by: Filipe Manana &lt;fdmanana@suse.com&gt;
Reviewed-by: David Sterba &lt;dsterba@suse.com&gt;
Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>btrfs: open code btrfs_ordered_inode_tree in btrfs_inode</title>
<updated>2023-10-12T14:44:16+00:00</updated>
<author>
<name>David Sterba</name>
<email>dsterba@suse.com</email>
</author>
<published>2023-09-27T12:22:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=54c65371464e6e676494473dd258d7c337146a35'/>
<id>54c65371464e6e676494473dd258d7c337146a35</id>
<content type='text'>
The structure btrfs_ordered_inode_tree is used only in one place, in
btrfs_inode. The structure itself has a 4 byte hole which is wasted
space.

Move the btrfs_ordered_inode_tree members to btrfs_inode with a common
prefix 'ordered_tree_' where the hole can be utilized and shrink inode
size.

Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The structure btrfs_ordered_inode_tree is used only in one place, in
btrfs_inode. The structure itself has a 4 byte hole which is wasted
space.

Move the btrfs_ordered_inode_tree members to btrfs_inode with a common
prefix 'ordered_tree_' where the hole can be utilized and shrink inode
size.

Signed-off-by: David Sterba &lt;dsterba@suse.com&gt;
</pre>
</div>
</content>
</entry>
</feed>
