From: Darrick J. Wong Date: Tue, 1 Jul 2025 17:45:13 +0000 (-0700) Subject: xfs: allow sysadmins to specify a maximum atomic write limit at mount time X-Git-Tag: v6.16.0~16 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1ba98d1f4fd9a484bc69420e449aaaa2848896cd;p=thirdparty%2Fxfsprogs-dev.git xfs: allow sysadmins to specify a maximum atomic write limit at mount time Source kernel commit: 4528b9052731f14c1a9be16b98e33c9401e6d1bc Introduce a mount option to allow sysadmins to specify the maximum size of an atomic write. If the filesystem can work with the supplied value, that becomes the new guaranteed maximum. The value mustn't be too big for the existing filesystem geometry (max write size, max AG/rtgroup size). We dynamically recompute the tr_atomic_write transaction reservation based on the given block size, check that the current log size isn't less than the new minimum log size constraints, and set a new maximum. The actual software atomic write max is still computed based off of tr_atomic_ioend the same way it has for the past few commits. Note also that xfs_calc_atomic_write_log_geometry is non-static because mkfs will need that. Signed-off-by: Darrick J. Wong Signed-off-by: John Garry Reviewed-by: John Garry --- diff --git a/include/platform_defs.h b/include/platform_defs.h index 9af7b431..74a00583 100644 --- a/include/platform_defs.h +++ b/include/platform_defs.h @@ -261,6 +261,20 @@ static inline bool __must_check __must_check_overflow(bool overflow) __builtin_add_overflow(__a, __b, __d); \ })) +/** + * check_mul_overflow() - Calculate multiplication with overflow checking + * @a: first factor + * @b: second factor + * @d: pointer to store product + * + * Returns true on wrap-around, false otherwise. + * + * *@d holds the results of the attempted multiplication, regardless of whether + * wrap-around occurred. + */ +#define check_mul_overflow(a, b, d) \ + __must_check_overflow(__builtin_mul_overflow(a, b, d)) + /** * abs_diff - return absolute value of the difference between the arguments * @a: the first argument diff --git a/include/xfs_trace.h b/include/xfs_trace.h index 965c109c..6bbf4007 100644 --- a/include/xfs_trace.h +++ b/include/xfs_trace.h @@ -65,6 +65,7 @@ #define trace_xfs_attr_rmtval_remove_return(...) ((void) 0) #define trace_xfs_calc_max_atomic_write_fsblocks(...) ((void) 0) +#define trace_xfs_calc_max_atomic_write_log_geometry(...) ((void) 0) #define trace_xfs_log_recover_item_add_cont(a,b,c,d) ((void) 0) #define trace_xfs_log_recover_item_add(a,b,c,d) ((void) 0) diff --git a/libxfs/xfs_trans_resv.c b/libxfs/xfs_trans_resv.c index ec61ddfb..b3b9d22b 100644 --- a/libxfs/xfs_trans_resv.c +++ b/libxfs/xfs_trans_resv.c @@ -1481,3 +1481,72 @@ xfs_calc_max_atomic_write_fsblocks( return ret; } + +/* + * Compute the log blocks and transaction reservation needed to complete an + * atomic write of a given number of blocks. Worst case, each block requires + * separate handling. A return value of 0 means something went wrong. + */ +xfs_extlen_t +xfs_calc_atomic_write_log_geometry( + struct xfs_mount *mp, + xfs_extlen_t blockcount, + unsigned int *new_logres) +{ + struct xfs_trans_res *curr_res = &M_RES(mp)->tr_atomic_ioend; + uint old_logres = curr_res->tr_logres; + unsigned int per_intent, step_size; + unsigned int logres; + xfs_extlen_t min_logblocks; + + ASSERT(blockcount > 0); + + xfs_calc_default_atomic_ioend_reservation(mp, M_RES(mp)); + + per_intent = xfs_calc_atomic_write_ioend_geometry(mp, &step_size); + + /* Check for overflows */ + if (check_mul_overflow(blockcount, per_intent, &logres) || + check_add_overflow(logres, step_size, &logres)) + return 0; + + curr_res->tr_logres = logres; + min_logblocks = xfs_log_calc_minimum_size(mp); + curr_res->tr_logres = old_logres; + + trace_xfs_calc_max_atomic_write_log_geometry(mp, per_intent, step_size, + blockcount, min_logblocks, logres); + + *new_logres = logres; + return min_logblocks; +} + +/* + * Compute the transaction reservation needed to complete an out of place + * atomic write of a given number of blocks. + */ +int +xfs_calc_atomic_write_reservation( + struct xfs_mount *mp, + xfs_extlen_t blockcount) +{ + unsigned int new_logres; + xfs_extlen_t min_logblocks; + + /* + * If the caller doesn't ask for a specific atomic write size, then + * use the defaults. + */ + if (blockcount == 0) { + xfs_calc_default_atomic_ioend_reservation(mp, M_RES(mp)); + return 0; + } + + min_logblocks = xfs_calc_atomic_write_log_geometry(mp, blockcount, + &new_logres); + if (!min_logblocks || min_logblocks > mp->m_sb.sb_logblocks) + return -EINVAL; + + M_RES(mp)->tr_atomic_ioend.tr_logres = new_logres; + return 0; +} diff --git a/libxfs/xfs_trans_resv.h b/libxfs/xfs_trans_resv.h index a6d303b8..336279e0 100644 --- a/libxfs/xfs_trans_resv.h +++ b/libxfs/xfs_trans_resv.h @@ -122,5 +122,9 @@ unsigned int xfs_calc_write_reservation_minlogsize(struct xfs_mount *mp); unsigned int xfs_calc_qm_dqalloc_reservation_minlogsize(struct xfs_mount *mp); xfs_extlen_t xfs_calc_max_atomic_write_fsblocks(struct xfs_mount *mp); +xfs_extlen_t xfs_calc_atomic_write_log_geometry(struct xfs_mount *mp, + xfs_extlen_t blockcount, unsigned int *new_logres); +int xfs_calc_atomic_write_reservation(struct xfs_mount *mp, + xfs_extlen_t blockcount); #endif /* __XFS_TRANS_RESV_H__ */