From: Hao Xu <howe...@tencent.com> Implement NOWAIT semantics for readdir. Return EAGAIN error to the caller if it would block, like failing to get locks, or going to do IO.
Co-developed-by: Dave Chinner <dchin...@redhat.com> Signed-off-by: Dave Chinner <dchin...@redhat.com> Signed-off-by: Hao Xu <howe...@tencent.com> [fixes deadlock issue, tweak code style] --- fs/xfs/libxfs/xfs_da_btree.c | 16 +++++++++++ fs/xfs/libxfs/xfs_da_btree.h | 1 + fs/xfs/libxfs/xfs_dir2_block.c | 7 ++--- fs/xfs/libxfs/xfs_dir2_priv.h | 2 +- fs/xfs/scrub/dir.c | 2 +- fs/xfs/scrub/readdir.c | 2 +- fs/xfs/xfs_dir2_readdir.c | 49 ++++++++++++++++++++++++++-------- fs/xfs/xfs_inode.c | 27 +++++++++++++++++++ fs/xfs/xfs_inode.h | 17 +++++++----- 9 files changed, 99 insertions(+), 24 deletions(-) diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c index e576560b46e9..7a1a0af24197 100644 --- a/fs/xfs/libxfs/xfs_da_btree.c +++ b/fs/xfs/libxfs/xfs_da_btree.c @@ -2643,16 +2643,32 @@ xfs_da_read_buf( struct xfs_buf_map map, *mapp = ↦ int nmap = 1; int error; + int buf_flags = 0; *bpp = NULL; error = xfs_dabuf_map(dp, bno, flags, whichfork, &mapp, &nmap); if (error || !nmap) goto out_free; + /* + * NOWAIT semantics mean we don't wait on the buffer lock nor do we + * issue IO for this buffer if it is not already in memory. Caller will + * retry. This will return -EAGAIN if the buffer is in memory and cannot + * be locked, and no buffer and no error if it isn't in memory. We + * translate both of those into a return state of -EAGAIN and *bpp = + * NULL. + */ + if (flags & XFS_DABUF_NOWAIT) + buf_flags |= XBF_TRYLOCK | XBF_INCORE; error = xfs_trans_read_buf_map(mp, tp, mp->m_ddev_targp, mapp, nmap, 0, &bp, ops); if (error) goto out_free; + if (!bp) { + ASSERT(flags & XFS_DABUF_NOWAIT); + error = -EAGAIN; + goto out_free; + } if (whichfork == XFS_ATTR_FORK) xfs_buf_set_ref(bp, XFS_ATTR_BTREE_REF); diff --git a/fs/xfs/libxfs/xfs_da_btree.h b/fs/xfs/libxfs/xfs_da_btree.h index ffa3df5b2893..32e7b1cca402 100644 --- a/fs/xfs/libxfs/xfs_da_btree.h +++ b/fs/xfs/libxfs/xfs_da_btree.h @@ -205,6 +205,7 @@ int xfs_da3_node_read_mapped(struct xfs_trans *tp, struct xfs_inode *dp, */ #define XFS_DABUF_MAP_HOLE_OK (1u << 0) +#define XFS_DABUF_NOWAIT (1u << 1) int xfs_da_grow_inode(xfs_da_args_t *args, xfs_dablk_t *new_blkno); int xfs_da_grow_inode_int(struct xfs_da_args *args, xfs_fileoff_t *bno, diff --git a/fs/xfs/libxfs/xfs_dir2_block.c b/fs/xfs/libxfs/xfs_dir2_block.c index 00f960a703b2..59b24a594add 100644 --- a/fs/xfs/libxfs/xfs_dir2_block.c +++ b/fs/xfs/libxfs/xfs_dir2_block.c @@ -135,13 +135,14 @@ int xfs_dir3_block_read( struct xfs_trans *tp, struct xfs_inode *dp, + unsigned int flags, struct xfs_buf **bpp) { struct xfs_mount *mp = dp->i_mount; xfs_failaddr_t fa; int err; - err = xfs_da_read_buf(tp, dp, mp->m_dir_geo->datablk, 0, bpp, + err = xfs_da_read_buf(tp, dp, mp->m_dir_geo->datablk, flags, bpp, XFS_DATA_FORK, &xfs_dir3_block_buf_ops); if (err || !*bpp) return err; @@ -380,7 +381,7 @@ xfs_dir2_block_addname( tp = args->trans; /* Read the (one and only) directory block into bp. */ - error = xfs_dir3_block_read(tp, dp, &bp); + error = xfs_dir3_block_read(tp, dp, 0, &bp); if (error) return error; @@ -695,7 +696,7 @@ xfs_dir2_block_lookup_int( dp = args->dp; tp = args->trans; - error = xfs_dir3_block_read(tp, dp, &bp); + error = xfs_dir3_block_read(tp, dp, 0, &bp); if (error) return error; diff --git a/fs/xfs/libxfs/xfs_dir2_priv.h b/fs/xfs/libxfs/xfs_dir2_priv.h index 7404a9ff1a92..7d4cf8a0f15b 100644 --- a/fs/xfs/libxfs/xfs_dir2_priv.h +++ b/fs/xfs/libxfs/xfs_dir2_priv.h @@ -51,7 +51,7 @@ extern int xfs_dir_cilookup_result(struct xfs_da_args *args, /* xfs_dir2_block.c */ extern int xfs_dir3_block_read(struct xfs_trans *tp, struct xfs_inode *dp, - struct xfs_buf **bpp); + unsigned int flags, struct xfs_buf **bpp); extern int xfs_dir2_block_addname(struct xfs_da_args *args); extern int xfs_dir2_block_lookup(struct xfs_da_args *args); extern int xfs_dir2_block_removename(struct xfs_da_args *args); diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c index 0b491784b759..5cc51f201bd7 100644 --- a/fs/xfs/scrub/dir.c +++ b/fs/xfs/scrub/dir.c @@ -313,7 +313,7 @@ xchk_directory_data_bestfree( /* dir block format */ if (lblk != XFS_B_TO_FSBT(mp, XFS_DIR2_DATA_OFFSET)) xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk); - error = xfs_dir3_block_read(sc->tp, sc->ip, &bp); + error = xfs_dir3_block_read(sc->tp, sc->ip, 0, &bp); } else { /* dir data format */ error = xfs_dir3_data_read(sc->tp, sc->ip, lblk, 0, &bp); diff --git a/fs/xfs/scrub/readdir.c b/fs/xfs/scrub/readdir.c index e51c1544be63..f0a727311632 100644 --- a/fs/xfs/scrub/readdir.c +++ b/fs/xfs/scrub/readdir.c @@ -101,7 +101,7 @@ xchk_dir_walk_block( unsigned int off, next_off, end; int error; - error = xfs_dir3_block_read(sc->tp, dp, &bp); + error = xfs_dir3_block_read(sc->tp, dp, 0, &bp); if (error) return error; diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c index 9f3ceb461515..dcdbd26e0402 100644 --- a/fs/xfs/xfs_dir2_readdir.c +++ b/fs/xfs/xfs_dir2_readdir.c @@ -149,6 +149,7 @@ xfs_dir2_block_getdents( struct xfs_da_geometry *geo = args->geo; unsigned int offset, next_offset; unsigned int end; + unsigned int flags = 0; /* * If the block number in the offset is out of range, we're done. @@ -156,7 +157,9 @@ xfs_dir2_block_getdents( if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk) return 0; - error = xfs_dir3_block_read(args->trans, dp, &bp); + if (ctx->flags & DIR_CONTEXT_F_NOWAIT) + flags |= XFS_DABUF_NOWAIT; + error = xfs_dir3_block_read(args->trans, dp, flags, &bp); if (error) return error; @@ -240,6 +243,7 @@ xfs_dir2_block_getdents( STATIC int xfs_dir2_leaf_readbuf( struct xfs_da_args *args, + struct dir_context *ctx, size_t bufsize, xfs_dir2_off_t *cur_off, xfs_dablk_t *ra_blk, @@ -258,10 +262,15 @@ xfs_dir2_leaf_readbuf( struct xfs_iext_cursor icur; int ra_want; int error = 0; - - error = xfs_iread_extents(args->trans, dp, XFS_DATA_FORK); - if (error) - goto out; + unsigned int flags = 0; + + if (ctx->flags & DIR_CONTEXT_F_NOWAIT) { + flags |= XFS_DABUF_NOWAIT; + } else { + error = xfs_iread_extents(args->trans, dp, XFS_DATA_FORK); + if (error) + goto out; + } /* * Look for mapped directory blocks at or above the current offset. @@ -280,7 +289,7 @@ xfs_dir2_leaf_readbuf( new_off = xfs_dir2_da_to_byte(geo, map.br_startoff); if (new_off > *cur_off) *cur_off = new_off; - error = xfs_dir3_data_read(args->trans, dp, map.br_startoff, 0, &bp); + error = xfs_dir3_data_read(args->trans, dp, map.br_startoff, flags, &bp); if (error) goto out; @@ -360,6 +369,7 @@ xfs_dir2_leaf_getdents( int byteoff; /* offset in current block */ unsigned int offset = 0; int error = 0; /* error return value */ + int written = 0; /* * If the offset is at or past the largest allowed value, @@ -391,10 +401,17 @@ xfs_dir2_leaf_getdents( bp = NULL; } - if (*lock_mode == 0) - *lock_mode = xfs_ilock_data_map_shared(dp); - error = xfs_dir2_leaf_readbuf(args, bufsize, &curoff, - &rablk, &bp); + if (*lock_mode == 0) { + *lock_mode = + xfs_ilock_data_map_shared_generic(dp, + ctx->flags & DIR_CONTEXT_F_NOWAIT); + if (!*lock_mode) { + error = -EAGAIN; + break; + } + } + error = xfs_dir2_leaf_readbuf(args, ctx, bufsize, + &curoff, &rablk, &bp); if (error || !bp) break; @@ -479,6 +496,7 @@ xfs_dir2_leaf_getdents( */ offset += length; curoff += length; + written += length; /* bufsize may have just been a guess; don't go negative */ bufsize = bufsize > length ? bufsize - length : 0; } @@ -492,6 +510,8 @@ xfs_dir2_leaf_getdents( ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff; if (bp) xfs_trans_brelse(args->trans, bp); + if (error == -EAGAIN && written > 0) + error = 0; return error; } @@ -514,6 +534,7 @@ xfs_readdir( unsigned int lock_mode; bool isblock; int error; + bool nowait; trace_xfs_readdir(dp); @@ -531,7 +552,11 @@ xfs_readdir( if (dp->i_df.if_format == XFS_DINODE_FMT_LOCAL) return xfs_dir2_sf_getdents(&args, ctx); - lock_mode = xfs_ilock_data_map_shared(dp); + nowait = ctx->flags & DIR_CONTEXT_F_NOWAIT; + lock_mode = xfs_ilock_data_map_shared_generic(dp, nowait); + if (!lock_mode) + return -EAGAIN; + error = xfs_dir2_isblock(&args, &isblock); if (error) goto out_unlock; @@ -546,5 +571,7 @@ xfs_readdir( out_unlock: if (lock_mode) xfs_iunlock(dp, lock_mode); + if (error == -EAGAIN) + ASSERT(nowait); return error; } diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 9e62cc500140..d088f7d0c23a 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -120,6 +120,33 @@ xfs_ilock_data_map_shared( return lock_mode; } +/* + * Similar to xfs_ilock_data_map_shared(), except that it will only try to lock + * the inode in shared mode if the extents are already in memory. If it fails to + * get the lock or has to do IO to read the extent list, fail the operation by + * returning 0 as the lock mode. + */ +uint +xfs_ilock_data_map_shared_nowait( + struct xfs_inode *ip) +{ + if (xfs_need_iread_extents(&ip->i_df)) + return 0; + if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) + return 0; + return XFS_ILOCK_SHARED; +} + +int +xfs_ilock_data_map_shared_generic( + struct xfs_inode *dp, + bool nowait) +{ + if (nowait) + return xfs_ilock_data_map_shared_nowait(dp); + return xfs_ilock_data_map_shared(dp); +} + uint xfs_ilock_attr_map_shared( struct xfs_inode *ip) diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index 7547caf2f2ab..ea206a5a27df 100644 --- a/fs/xfs/xfs_inode.h +++ b/fs/xfs/xfs_inode.h @@ -490,13 +490,16 @@ int xfs_rename(struct mnt_idmap *idmap, struct xfs_name *target_name, struct xfs_inode *target_ip, unsigned int flags); -void xfs_ilock(xfs_inode_t *, uint); -int xfs_ilock_nowait(xfs_inode_t *, uint); -void xfs_iunlock(xfs_inode_t *, uint); -void xfs_ilock_demote(xfs_inode_t *, uint); -bool xfs_isilocked(struct xfs_inode *, uint); -uint xfs_ilock_data_map_shared(struct xfs_inode *); -uint xfs_ilock_attr_map_shared(struct xfs_inode *); +void xfs_ilock(struct xfs_inode *ip, uint lockmode); +int xfs_ilock_nowait(struct xfs_inode *ip, uint lockmode); +void xfs_iunlock(struct xfs_inode *ip, uint lockmode); +void xfs_ilock_demote(struct xfs_inode *ip, uint lockmode); +bool xfs_isilocked(struct xfs_inode *ip, uint lockmode); +uint xfs_ilock_data_map_shared(struct xfs_inode *ip); +uint xfs_ilock_data_map_shared_nowait(struct xfs_inode *ip); +int xfs_ilock_data_map_shared_generic(struct xfs_inode *ip, + bool nowait); +uint xfs_ilock_attr_map_shared(struct xfs_inode *ip); uint xfs_ip2xflags(struct xfs_inode *); int xfs_ifree(struct xfs_trans *, struct xfs_inode *); -- 2.25.1