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d8d222e09d
Recently xfs/513 started failing on my test machines testing "-o
ro,norecovery" mount options. This was being emitted in dmesg:
[ 9906.932724] XFS (pmem0): no-recovery mounts must be read-only.
Turns out, readonly mounts with the fsopen()/fsconfig() mount API
have been busted since day zero. It's only taken 5 years for debian
unstable to start using this "new" mount API, and shortly after this
I noticed xfs/513 had started to fail as per above.
The syscall trace is:
fsopen("xfs", FSOPEN_CLOEXEC) = 3
mount_setattr(-1, NULL, 0, NULL, 0) = -1 EINVAL (Invalid argument)
.....
fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/pmem0", 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0
fsconfig(3, FSCONFIG_SET_FLAG, "norecovery", NULL, 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)
close(3) = 0
Showing that the actual mount instantiation (FSCONFIG_CMD_CREATE) is
what threw out the error.
During mount instantiation, we call xfs_fs_validate_params() which
does:
/* No recovery flag requires a read-only mount */
if (xfs_has_norecovery(mp) && !xfs_is_readonly(mp)) {
xfs_warn(mp, "no-recovery mounts must be read-only.");
return -EINVAL;
}
and xfs_is_readonly() checks internal mount flags for read only
state. This state is set in xfs_init_fs_context() from the
context superblock flag state:
/*
* Copy binary VFS mount flags we are interested in.
*/
if (fc->sb_flags & SB_RDONLY)
set_bit(XFS_OPSTATE_READONLY, &mp->m_opstate);
With the old mount API, all of the VFS specific superblock flags
had already been parsed and set before xfs_init_fs_context() is
called, so this all works fine.
However, in the brave new fsopen/fsconfig world,
xfs_init_fs_context() is called from fsopen() context, before any
VFS superblock have been set or parsed. Hence if we use fsopen(),
the internal XFS readonly state is *never set*. Hence anything that
depends on xfs_is_readonly() actually returning true for read only
mounts is broken if fsopen() has been used to mount the filesystem.
Fix this by moving this internal state initialisation to
xfs_fs_fill_super() before we attempt to validate the parameters
that have been set prior to the FSCONFIG_CMD_CREATE call being made.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Fixes:
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
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the problems which may result by upgrading your kernel.