On Sun, Jun 23, 2024 at 07:34:52AM +0200, Christoph Hellwig wrote: > From: "Darrick J. Wong" <djwong@xxxxxxxxxx> > > Certain workloads fragment files on XFS very badly, such as a software > package that creates a number of threads, each of which repeatedly run > the sequence: open a file, perform a synchronous write, and close the > file, which defeats the speculative preallocation mechanism. We work > around this problem by only deleting posteof blocks the /first/ time a > file is closed to preserve the behavior that unpacking a tarball lays > out files one after the other with no gaps. > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > [hch: rebased, updated comment, renamed the flag] > Signed-off-by: Christoph Hellwig <hch@xxxxxx> Someone please review this? The last person to try was Dave, five years ago, and I do not know if he ever saw what it did to various workloads. https://lore.kernel.org/linux-xfs/20190315034237.GL23020@dastard/ --D > --- > fs/xfs/xfs_file.c | 32 +++++++++++--------------------- > fs/xfs/xfs_inode.h | 4 ++-- > 2 files changed, 13 insertions(+), 23 deletions(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 8d70171678fe24..de52aceabebc27 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1215,15 +1215,21 @@ xfs_file_release( > * exposed to that problem. > */ > if (xfs_iflags_test_and_clear(ip, XFS_ITRUNCATED)) { > - xfs_iflags_clear(ip, XFS_IDIRTY_RELEASE); > + xfs_iflags_clear(ip, XFS_EOFBLOCKS_RELEASED); > if (ip->i_delayed_blks > 0) > filemap_flush(inode->i_mapping); > } > > /* > * XFS aggressively preallocates post-EOF space to generate contiguous > - * allocations for writers that append to the end of the file and we > - * try to free these when an open file context is released. > + * allocations for writers that append to the end of the file. > + * > + * To support workloads that close and reopen the file frequently, these > + * preallocations usually persist after a close unless it is the first > + * close for the inode. This is a tradeoff to generate tightly packed > + * data layouts for unpacking tarballs or similar archives that write > + * one file after another without going back to it while keeping the > + * preallocation for files that have recurring open/write/close cycles. > * > * There is no point in freeing blocks here for open but unlinked files > * as they will be taken care of by the inactivation path soon. > @@ -1241,25 +1247,9 @@ xfs_file_release( > (file->f_mode & FMODE_WRITE) && > xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) { > if (xfs_can_free_eofblocks(ip) && > - !xfs_iflags_test(ip, XFS_IDIRTY_RELEASE)) { > - /* > - * Check if the inode is being opened, written and > - * closed frequently and we have delayed allocation > - * blocks outstanding (e.g. streaming writes from the > - * NFS server), truncating the blocks past EOF will > - * cause fragmentation to occur. > - * > - * In this case don't do the truncation, but we have to > - * be careful how we detect this case. Blocks beyond EOF > - * show up as i_delayed_blks even when the inode is > - * clean, so we need to truncate them away first before > - * checking for a dirty release. Hence on the first > - * dirty close we will still remove the speculative > - * allocation, but after that we will leave it in place. > - */ > + !xfs_iflags_test(ip, XFS_EOFBLOCKS_RELEASED)) { > xfs_free_eofblocks(ip); > - if (ip->i_delayed_blks) > - xfs_iflags_set(ip, XFS_IDIRTY_RELEASE); > + xfs_iflags_set(ip, XFS_EOFBLOCKS_RELEASED); > } > xfs_iunlock(ip, XFS_IOLOCK_EXCL); > } > diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h > index ae9851226f9913..548a4f00bcae1b 100644 > --- a/fs/xfs/xfs_inode.h > +++ b/fs/xfs/xfs_inode.h > @@ -336,7 +336,7 @@ static inline bool xfs_inode_has_bigrtalloc(struct xfs_inode *ip) > #define XFS_INEW (1 << 3) /* inode has just been allocated */ > #define XFS_IPRESERVE_DM_FIELDS (1 << 4) /* has legacy DMAPI fields set */ > #define XFS_ITRUNCATED (1 << 5) /* truncated down so flush-on-close */ > -#define XFS_IDIRTY_RELEASE (1 << 6) /* dirty release already seen */ > +#define XFS_EOFBLOCKS_RELEASED (1 << 6) /* eofblocks were freed in ->release */ > #define XFS_IFLUSHING (1 << 7) /* inode is being flushed */ > #define __XFS_IPINNED_BIT 8 /* wakeup key for zero pin count */ > #define XFS_IPINNED (1 << __XFS_IPINNED_BIT) > @@ -383,7 +383,7 @@ static inline bool xfs_inode_has_bigrtalloc(struct xfs_inode *ip) > */ > #define XFS_IRECLAIM_RESET_FLAGS \ > (XFS_IRECLAIMABLE | XFS_IRECLAIM | \ > - XFS_IDIRTY_RELEASE | XFS_ITRUNCATED | XFS_NEED_INACTIVE | \ > + XFS_EOFBLOCKS_RELEASED | XFS_ITRUNCATED | XFS_NEED_INACTIVE | \ > XFS_INACTIVATING | XFS_IQUOTAUNCHECKED) > > /* > -- > 2.43.0 > >
