6.15-stable review patch. If anyone has any objections, please let me know.
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From: Dave Chinner dchinner@redhat.com
commit 23be716b1c4f3f3a6c00ee38d51a57ef7db9ef7d upstream.
When running fstrim immediately after mounting a V4 filesystem, the fstrim fails to trim all the free space in the filesystem. It only trims the first extent in the by-size free space tree in each AG and then returns. If a second fstrim is then run, it runs correctly and the entire free space in the filesystem is iterated and discarded correctly.
The problem lies in the setup of the trim cursor - it assumes that pag->pagf_longest is valid without either reading the AGF first or checking if xfs_perag_initialised_agf(pag) is true or not.
As a result, when a filesystem is mounted without reading the AGF (e.g. a clean mount on a v4 filesystem) and the first operation is a fstrim call, pag->pagf_longest is zero and so the free extent search starts at the wrong end of the by-size btree and exits after discarding the first record in the tree.
Fix this by deferring the initialisation of tcur->count to after we have locked the AGF and guaranteed that the perag is properly initialised. We trigger this on tcur->count == 0 after locking the AGF, as this will only occur on the first call to xfs_trim_gather_extents() for each AG. If we need to iterate, tcur->count will be set to the length of the record we need to restart at, so we can use this to ensure we only sample a valid pag->pagf_longest value for the iteration.
Signed-off-by: Dave Chinner dchinner@redhat.com Reviewed-by: Bill O'Donnell bodonnel@redhat.com Reviewed-by: Darrick J. Wong djwong@kernel.org Fixes: 89cfa899608f ("xfs: reduce AGF hold times during fstrim operations") Cc: stable@vger.kernel.org # v6.6 Signed-off-by: Carlos Maiolino cem@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/xfs/xfs_discard.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
--- a/fs/xfs/xfs_discard.c +++ b/fs/xfs/xfs_discard.c @@ -167,6 +167,14 @@ xfs_discard_extents( return error; }
+/* + * Care must be taken setting up the trim cursor as the perags may not have been + * initialised when the cursor is initialised. e.g. a clean mount which hasn't + * read in AGFs and the first operation run on the mounted fs is a trim. This + * can result in perag fields that aren't initialised until + * xfs_trim_gather_extents() calls xfs_alloc_read_agf() to lock down the AG for + * the free space search. + */ struct xfs_trim_cur { xfs_agblock_t start; xfs_extlen_t count; @@ -204,6 +212,14 @@ xfs_trim_gather_extents( if (error) goto out_trans_cancel;
+ /* + * First time through tcur->count will not have been initialised as + * pag->pagf_longest is not guaranteed to be valid before we read + * the AGF buffer above. + */ + if (!tcur->count) + tcur->count = pag->pagf_longest; + if (tcur->by_bno) { /* sub-AG discard request always starts at tcur->start */ cur = xfs_bnobt_init_cursor(mp, tp, agbp, pag); @@ -350,7 +366,6 @@ xfs_trim_perag_extents( { struct xfs_trim_cur tcur = { .start = start, - .count = pag->pagf_longest, .end = end, .minlen = minlen, };