| Message ID | 164755206098.4194202.17244831596965430593.stgit@magnolia (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | xfs: fix incorrect reserve pool calculations and reporting | expand |
On Thu, Mar 17, 2022 at 02:21:01PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > Currently, we use this undocumented macro to encode the minimum number > of blocks needed to replenish a completely empty AGFL when an AG is > nearly full. This has lead to confusion on the part of the maintainers, > so let's document what the value actually means, and move it to > xfs_alloc.c since it's not used outside of that module. > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > --- Reviewed-by: Brian Foster <bfoster@redhat.com> > fs/xfs/libxfs/xfs_alloc.c | 23 ++++++++++++++++++----- > fs/xfs/libxfs/xfs_alloc.h | 1 - > 2 files changed, 18 insertions(+), 6 deletions(-) > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > index 353e53b892e6..b0678e96ce61 100644 > --- a/fs/xfs/libxfs/xfs_alloc.c > +++ b/fs/xfs/libxfs/xfs_alloc.c > @@ -82,6 +82,19 @@ xfs_prealloc_blocks( > } > > /* > + * The number of blocks per AG that we withhold from xfs_mod_fdblocks to > + * guarantee that we can refill the AGFL prior to allocating space in a nearly > + * full AG. We require two blocks per free space btree because free space > + * btrees shrink to a single block as the AG fills up, and any allocation can > + * cause a btree split. The rmap btree uses a per-AG reservation to withhold > + * space from xfs_mod_fdblocks, so we do not account for that here. > + */ > +#define XFS_ALLOCBT_AGFL_RESERVE 4 > + > +/* > + * Compute the number of blocks that we set aside to guarantee the ability to > + * refill the AGFL and handle a full bmap btree split. > + * > * In order to avoid ENOSPC-related deadlock caused by out-of-order locking of > * AGF buffer (PV 947395), we place constraints on the relationship among > * actual allocations for data blocks, freelist blocks, and potential file data > @@ -93,14 +106,14 @@ xfs_prealloc_blocks( > * extents need to be actually allocated. To get around this, we explicitly set > * aside a few blocks which will not be reserved in delayed allocation. > * > - * We need to reserve 4 fsbs _per AG_ for the freelist and 4 more to handle a > - * potential split of the file's bmap btree. > + * For each AG, we need to reserve enough blocks to replenish a totally empty > + * AGFL and 4 more to handle a potential split of the file's bmap btree. > */ > unsigned int > xfs_alloc_set_aside( > struct xfs_mount *mp) > { > - return mp->m_sb.sb_agcount * (XFS_ALLOC_AGFL_RESERVE + 4); > + return mp->m_sb.sb_agcount * (XFS_ALLOCBT_AGFL_RESERVE + 4); > } > > /* > @@ -124,12 +137,12 @@ xfs_alloc_ag_max_usable( > unsigned int blocks; > > blocks = XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)); /* ag headers */ > - blocks += XFS_ALLOC_AGFL_RESERVE; > + blocks += XFS_ALLOCBT_AGFL_RESERVE; > blocks += 3; /* AGF, AGI btree root blocks */ > if (xfs_has_finobt(mp)) > blocks++; /* finobt root block */ > if (xfs_has_rmapbt(mp)) > - blocks++; /* rmap root block */ > + blocks++; /* rmap root block */ > if (xfs_has_reflink(mp)) > blocks++; /* refcount root block */ > > diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h > index 1c14a0b1abea..d4c057b764f9 100644 > --- a/fs/xfs/libxfs/xfs_alloc.h > +++ b/fs/xfs/libxfs/xfs_alloc.h > @@ -88,7 +88,6 @@ typedef struct xfs_alloc_arg { > #define XFS_ALLOC_NOBUSY (1 << 2)/* Busy extents not allowed */ > > /* freespace limit calculations */ > -#define XFS_ALLOC_AGFL_RESERVE 4 > unsigned int xfs_alloc_set_aside(struct xfs_mount *mp); > unsigned int xfs_alloc_ag_max_usable(struct xfs_mount *mp); > >
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 353e53b892e6..b0678e96ce61 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -82,6 +82,19 @@ xfs_prealloc_blocks( } /* + * The number of blocks per AG that we withhold from xfs_mod_fdblocks to + * guarantee that we can refill the AGFL prior to allocating space in a nearly + * full AG. We require two blocks per free space btree because free space + * btrees shrink to a single block as the AG fills up, and any allocation can + * cause a btree split. The rmap btree uses a per-AG reservation to withhold + * space from xfs_mod_fdblocks, so we do not account for that here. + */ +#define XFS_ALLOCBT_AGFL_RESERVE 4 + +/* + * Compute the number of blocks that we set aside to guarantee the ability to + * refill the AGFL and handle a full bmap btree split. + * * In order to avoid ENOSPC-related deadlock caused by out-of-order locking of * AGF buffer (PV 947395), we place constraints on the relationship among * actual allocations for data blocks, freelist blocks, and potential file data @@ -93,14 +106,14 @@ xfs_prealloc_blocks( * extents need to be actually allocated. To get around this, we explicitly set * aside a few blocks which will not be reserved in delayed allocation. * - * We need to reserve 4 fsbs _per AG_ for the freelist and 4 more to handle a - * potential split of the file's bmap btree. + * For each AG, we need to reserve enough blocks to replenish a totally empty + * AGFL and 4 more to handle a potential split of the file's bmap btree. */ unsigned int xfs_alloc_set_aside( struct xfs_mount *mp) { - return mp->m_sb.sb_agcount * (XFS_ALLOC_AGFL_RESERVE + 4); + return mp->m_sb.sb_agcount * (XFS_ALLOCBT_AGFL_RESERVE + 4); } /* @@ -124,12 +137,12 @@ xfs_alloc_ag_max_usable( unsigned int blocks; blocks = XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)); /* ag headers */ - blocks += XFS_ALLOC_AGFL_RESERVE; + blocks += XFS_ALLOCBT_AGFL_RESERVE; blocks += 3; /* AGF, AGI btree root blocks */ if (xfs_has_finobt(mp)) blocks++; /* finobt root block */ if (xfs_has_rmapbt(mp)) - blocks++; /* rmap root block */ + blocks++; /* rmap root block */ if (xfs_has_reflink(mp)) blocks++; /* refcount root block */ diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h index 1c14a0b1abea..d4c057b764f9 100644 --- a/fs/xfs/libxfs/xfs_alloc.h +++ b/fs/xfs/libxfs/xfs_alloc.h @@ -88,7 +88,6 @@ typedef struct xfs_alloc_arg { #define XFS_ALLOC_NOBUSY (1 << 2)/* Busy extents not allowed */ /* freespace limit calculations */ -#define XFS_ALLOC_AGFL_RESERVE 4 unsigned int xfs_alloc_set_aside(struct xfs_mount *mp); unsigned int xfs_alloc_ag_max_usable(struct xfs_mount *mp);