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Brian Behlendorf
cfc9a5c88f
Disable the normal reclaim path for zpl_putpage(). This ensures that all memory allocations under this call path will never enter direct reclaim. If this were to happen the VM might try to write out additional pages by calling zpl_putpage() again resulting in a deadlock. This sitution is typically handled in Linux by marking each offending allocation GFP_NOFS. However, since much of the code used is common it makes more sense to use PF_MEMALLOC to flag the entire call tree. Alternately, the code could be updated to pass the needed allocation flags but that's a more invasive change. The following example of the above described deadlock was triggered by test 074 in the xfstest suite. Call Trace: [<ffffffff814dcdb2>] down_write+0x32/0x40 [<ffffffffa05af6e4>] dnode_new_blkid+0x94/0x2d0 [zfs] [<ffffffffa0597d66>] dbuf_dirty+0x556/0x750 [zfs] [<ffffffffa05987d1>] dmu_buf_will_dirty+0x81/0xd0 [zfs] [<ffffffffa059ee70>] dmu_write+0x90/0x170 [zfs] [<ffffffffa0611afe>] zfs_putpage+0x2ce/0x360 [zfs] [<ffffffffa062875e>] zpl_putpage+0x1e/0x60 [zfs] [<ffffffffa06287b2>] zpl_writepage+0x12/0x20 [zfs] [<ffffffff8115f907>] writeout+0xa7/0xd0 [<ffffffff8115fa6b>] move_to_new_page+0x13b/0x170 [<ffffffff8115fed4>] migrate_pages+0x434/0x4c0 [<ffffffff811559ab>] compact_zone+0x4fb/0x780 [<ffffffff81155ed1>] compact_zone_order+0xa1/0xe0 [<ffffffff8115602c>] try_to_compact_pages+0x11c/0x190 [<ffffffff811200bb>] __alloc_pages_nodemask+0x5eb/0x8b0 [<ffffffff8115464a>] alloc_pages_current+0xaa/0x110 [<ffffffff8111e36e>] __get_free_pages+0xe/0x50 [<ffffffffa03f0e2f>] kv_alloc+0x3f/0xb0 [spl] [<ffffffffa03f11d9>] spl_kmem_cache_alloc+0x339/0x660 [spl] [<ffffffffa05950b3>] dbuf_create+0x43/0x370 [zfs] [<ffffffffa0596fb1>] __dbuf_hold_impl+0x241/0x480 [zfs] [<ffffffffa0597276>] dbuf_hold_impl+0x86/0xc0 [zfs] [<ffffffffa05977ff>] dbuf_hold_level+0x1f/0x30 [zfs] [<ffffffffa05a9dde>] dmu_tx_check_ioerr+0x4e/0x110 [zfs] [<ffffffffa05aa1f9>] dmu_tx_count_write+0x359/0x6f0 [zfs] [<ffffffffa05aa5df>] dmu_tx_hold_write+0x4f/0x70 [zfs] [<ffffffffa0611a6d>] zfs_putpage+0x23d/0x360 [zfs] [<ffffffffa062875e>] zpl_putpage+0x1e/0x60 [zfs] [<ffffffff811221f9>] write_cache_pages+0x1c9/0x4a0 [<ffffffffa0628738>] zpl_writepages+0x18/0x20 [zfs] [<ffffffff81122521>] do_writepages+0x21/0x40 [<ffffffff8119bbbd>] writeback_single_inode+0xdd/0x2c0 [<ffffffff8119bfbe>] writeback_sb_inodes+0xce/0x180 [<ffffffff8119c11b>] writeback_inodes_wb+0xab/0x1b0 [<ffffffff8119c4bb>] wb_writeback+0x29b/0x3f0 [<ffffffff8119c6cb>] wb_do_writeback+0xbb/0x240 [<ffffffff811308ea>] bdi_forker_task+0x6a/0x310 [<ffffffff8108ddf6>] kthread+0x96/0xa0 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #327
Native ZFS for Linux! ZFS is an advanced file system and volume manager which was originally developed for Solaris. It has been successfully ported to FreeBSD and now there is a functional Linux ZFS kernel port too. The port currently includes a fully functional and stable SPA, DMU, and ZVOL with a ZFS Posix Layer (ZPL) on the way!
$ ./configure
$ make pkg
Full documentation for building, configuring, and using ZFS can be found at: http://zfsonlinux.org