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Freeing an extent in XFS involves logging an EFI (extent free intention), freeing the actual extent, and logging an EFD (extent free done). The EFI object is created with a reference count of 2: one for the current transaction and one for the subsequently created EFD. Under normal circumstances, the first reference is dropped when the EFI is unpinned and the second reference is dropped when the EFD is committed to the on-disk log. In event of errors or filesystem shutdown, there are various potential cleanup scenarios depending on the state of the EFI/EFD. The cleanup scenarios are confusing and racy, as demonstrated by the following test sequence: # mount $dev $mnt # fsstress -d $mnt -n 99999 -p 16 -z -f fallocate=1 \ -f punch=1 -f creat=1 -f unlink=1 & # sleep 5 # killall -9 fsstress; wait # godown -f $mnt # umount ... in which the final umount can hang due to the AIL being pinned indefinitely by one or more EFI items. This can occur due to several conditions. For example, if the shutdown occurs after the EFI is committed to the on-disk log and the EFD committed to the CIL, but before the EFD committed to the log, the EFD iop_committed() abort handler does not drop its reference to the EFI. Alternatively, manual error injection in the xfs_bmap_finish() codepath shows that if an error occurs after the EFI transaction is committed but before the EFD is constructed and logged, the EFI is never released from the AIL. Update the EFI/EFD item handling code to use a more straightforward and reliable approach to error handling. If an error occurs after the EFI transaction is committed and before the EFD is constructed, release the EFI explicitly from xfs_bmap_finish(). If the EFI transaction is cancelled, release the EFI in the unlock handler. Once the EFD is constructed, it is responsible for releasing the EFI under any circumstances (including whether the EFI item aborts due to log I/O error). Update the EFD item handlers to release the EFI if the transaction is cancelled or aborts due to log I/O error. Finally, update xfs_bmap_finish() to log at least one EFD extent to the transaction before xfs_free_extent() errors are handled to ensure the transaction is dirty and EFD item error handling is triggered. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
102 lines
3.7 KiB
C
102 lines
3.7 KiB
C
/*
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* Copyright (c) 2000,2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef __XFS_EXTFREE_ITEM_H__
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#define __XFS_EXTFREE_ITEM_H__
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/* kernel only EFI/EFD definitions */
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struct xfs_mount;
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struct kmem_zone;
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/*
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* Max number of extents in fast allocation path.
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*/
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#define XFS_EFI_MAX_FAST_EXTENTS 16
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/*
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* Define EFI flag bits. Manipulated by set/clear/test_bit operators.
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*/
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#define XFS_EFI_RECOVERED 1
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/*
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* This is the "extent free intention" log item. It is used to log the fact
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* that some extents need to be free. It is used in conjunction with the
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* "extent free done" log item described below.
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*
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* The EFI is reference counted so that it is not freed prior to both the EFI
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* and EFD being committed and unpinned. This ensures the EFI is inserted into
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* the AIL even in the event of out of order EFI/EFD processing. In other words,
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* an EFI is born with two references:
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*
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* 1.) an EFI held reference to track EFI AIL insertion
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* 2.) an EFD held reference to track EFD commit
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*
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* On allocation, both references are the responsibility of the caller. Once the
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* EFI is added to and dirtied in a transaction, ownership of reference one
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* transfers to the transaction. The reference is dropped once the EFI is
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* inserted to the AIL or in the event of failure along the way (e.g., commit
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* failure, log I/O error, etc.). Note that the caller remains responsible for
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* the EFD reference under all circumstances to this point. The caller has no
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* means to detect failure once the transaction is committed, however.
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* Therefore, an EFD is required after this point, even in the event of
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* unrelated failure.
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*
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* Once an EFD is allocated and dirtied in a transaction, reference two
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* transfers to the transaction. The EFD reference is dropped once it reaches
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* the unpin handler. Similar to the EFI, the reference also drops in the event
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* of commit failure or log I/O errors. Note that the EFD is not inserted in the
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* AIL, so at this point both the EFI and EFD are freed.
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*/
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typedef struct xfs_efi_log_item {
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xfs_log_item_t efi_item;
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atomic_t efi_refcount;
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atomic_t efi_next_extent;
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unsigned long efi_flags; /* misc flags */
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xfs_efi_log_format_t efi_format;
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} xfs_efi_log_item_t;
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/*
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* This is the "extent free done" log item. It is used to log
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* the fact that some extents earlier mentioned in an efi item
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* have been freed.
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*/
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typedef struct xfs_efd_log_item {
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xfs_log_item_t efd_item;
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xfs_efi_log_item_t *efd_efip;
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uint efd_next_extent;
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xfs_efd_log_format_t efd_format;
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} xfs_efd_log_item_t;
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/*
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* Max number of extents in fast allocation path.
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*/
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#define XFS_EFD_MAX_FAST_EXTENTS 16
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extern struct kmem_zone *xfs_efi_zone;
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extern struct kmem_zone *xfs_efd_zone;
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xfs_efi_log_item_t *xfs_efi_init(struct xfs_mount *, uint);
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xfs_efd_log_item_t *xfs_efd_init(struct xfs_mount *, xfs_efi_log_item_t *,
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uint);
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int xfs_efi_copy_format(xfs_log_iovec_t *buf,
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xfs_efi_log_format_t *dst_efi_fmt);
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void xfs_efi_item_free(xfs_efi_log_item_t *);
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void xfs_efi_release(struct xfs_efi_log_item *);
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#endif /* __XFS_EXTFREE_ITEM_H__ */
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